CN101873918B - Rotary valve assembly for an injection nozzle - Google Patents

Abstract

A rotary valve assembly (30, 130, 230, 330, 430, 530) for an injection unit (20) is provided, having a valve body (32, 132), defining a melt channel (28) for a working fluid. At least one end cap (38, 138, 238) is mounted to the valve body (32, 132), the valve body (32, 132) and the at least one end cap (38, 138, 238) cooperatively defining a valve seat (36) intersecting the melt channel (28) in a generally traverse direction, the valve seat (36) having a wider portion (42) and a narrower portion (44). A spool (54, 154) defines an orifice (70), the spool (54, 154) being rotatably mounted within the valve seat (36), and is movable between an open position where the orifice (70) is aligned with the melt channel (28) and a closed position where the orifice (70) is misaligned with the melt channel.

Description

Rotary Valve Assembly for Injection Nozzles

technical field

The present invention relates generally to molding systems; more particularly, the present invention relates to a rotary valve assembly for an injection nozzle of a molding system.

Background technique

The injection molding process usually involves preparing a polymeric material in the injection unit of an injection molding machine, injecting the now molten material under pressure into a water-cooled closed and clamped mold, allowing the material to solidify in its molded shape , opens the mold and ejects the part before starting the next cycle. The polymeric material is usually supplied from a hopper to the injection unit in pellet or powder form. Injection units typically use a feed screw to convert a solid polymeric material into a molten material, which is then injected under pressure from the feed screw or plunger unit into a hot runner or other molding system. A shut-off valve assembly is often provided to stop and start the flow of molten material from the barrel to the molding system.

Numerous types of injection units are available, including sliding piston valves and rotary valves. An example of a prior art sliding piston valve assembly for an injection unit can be found in US Patent No. 4,140,238 to Dawson (published February 20, 1979). An example of a prior art rotary valve assembly for an injection unit can be found in US Patent No. 4,054,273 to Neuman (published October 18, 1977).

Efforts have been made to improve rotary valve assemblies. European Patent No. 0494304B1 to YOKOTA, Akira et al. entitled "Rotary Valve of Injection Molding Machine" (published on September 7, 1994) teaches an injection molding machine A rotary valve assembly having a cylindrical valve cavity formed in a flow passage, the flow passage is filled with molten resin under pressure, and the molten resin flows from the screw side to the nozzle side through the flow passage, wherein the cylindrical valve cavity is surrounded The axis of the cylindrical valve body (which has a through hole radially through the valve body for ensuring unobstructed flow through the flow passage, so that the through hole can be aligned with the axis of the cylindrical valve cavity) in a slidable manner In the valve cavity, and circumferential grooves are formed on both sides of the through hole in the circumferential direction and on the peripheral surface of the cylindrical valve body along the axis thereof, so that even a small driving torque can actuate the cylindrical valve body.

Japanese Patent No. 09123218A to MASATAKA et al. entitled "Shutoff Nozzle for Injection Molding Machine" (published on May 13, 1997) teaches the following: In an extrusion molding machine cut-off nozzle that rotates between a position where the molten resin passage is connected and a position where the molten resin passage is cut off, in the A housing is provided at a position in which a rotating member is provided at the end of a cylindrical rotary valve which has a through hole inside the housing and is inserted in a freely rotatable manner; arranged in a direction intersecting the nozzle to temporarily allow A pressure reducing valve that leaves molten resin on the hot runner.

Contents of the invention

According to a first broad aspect of the present invention there is provided a rotary valve assembly (30, 130, 230, 330, 430, 530) for an injection unit (20) comprising:

A valve body (32, 132) delimiting a melt channel (28) for a working fluid and an outer bore (34) laterally separating said melt channel (28) point;

at least one end cap (38, 138, 238) mounted to said valve body (32, 132) and defining an insert portion (40, 140) extending into said outer bore (34), said valve body ( 32, 132) and said at least one end cap (38, 138, 238) cooperatively define a valve seat (36) transversely intersecting said melt channel (28), said valve seat (36) having a wider portion (42) bounded by a portion of said outer bore (34) and a narrower portion (44) bounded by an inner bore (48) of said at least one end cap (38, 138, 238) ;as well as

a spool (54, 154) defining an orifice (70), said spool (54, 154) being rotatably mounted within said valve seat (36) and between said orifice (70) and said The open position of the melt channel (28) aligned for rapid transfer of the working fluid through the melt channel (28) is not aligned with the orifice (70) and the melt channel (28) aligned to prevent said rapid transfer of said working fluid through said melt channel (28) from moving between closed positions; and

wherein said wider portion (42) of said valve seat is shorter than said narrower portion (44) of said valve seat.

Description of drawings

A better understanding of non-limiting embodiments of the invention, including alternatives and/or variations thereof, may be obtained by reference to the detailed description of non-limiting embodiments of the invention together with the following drawings.

Figure 1 shows a perspective view of a part of an injection unit for a molding system according to a first non-limiting embodiment of the invention;

Figure 2 shows a side cross-sectional view of the injection unit shown in Figure 1;

Figure 3 shows a front cross-sectional view of a rotary valve assembly for the injection unit shown in Figure 1;

Figure 4 shows a simplified schematic front cross-sectional view of the rotary valve assembly shown in Figure 3;

5A and 5B show simplified schematic side cross-sectional views of the rotary valve assembly shown in FIG. 3 taken along lines AA and BB, respectively;

6A and 6B show opposing side views of a rotary valve assembly according to a second non-limiting embodiment of the present invention;

Figure 7 shows a front cross-sectional view of the rotary valve assembly shown in Figures 6A and 6B;

Figure 8 shows a perspective view of a spool for a rotary valve assembly according to a third non-limiting embodiment of the present invention;

Figure 9 shows a cross-section of a portion of a rotary valve assembly according to a fourth non-limiting embodiment of the invention;

Figure 10 shows a perspective view of a spool for the rotary valve assembly shown in Figure 9;

Figure 11 shows a perspective view of a piston ring for the rotary valve assembly shown in Figure 9;

Figure 12 shows a front cross-sectional view of a wedging assembly for a rotary valve assembly according to a fifth non-limiting embodiment of the present invention;

Figure 13 shows a front cross-sectional view of a rotary valve assembly according to a sixth non-limiting embodiment of the present invention; and

Figure 14 shows a front cross-sectional view of a rotary valve assembly according to a seventh non-limiting embodiment of the present invention.

Detailed ways

Referring now to FIGS. 1 to 4 , an injection unit for a molding system according to a first non-limiting embodiment is generally shown at 20 . The injection unit 20 comprises an extrusion barrel 22 adapted to receive a screw (not shown), a closing ram 24 closing off the end of the extrusion barrel 22, and a nozzle 26, all aligned in a coaxial manner. Delimited therebetween is a melt channel 28 extending through the barrel 22 , the closing head 24 and the nozzle 26 . A working fluid, typically a molten material such as PET resin, is rapidly passed through the melt channel 28 (from the barrel 22, through the closing head 24 and then exiting through the outlet 29 on the nozzle 26).

A rotary valve combination is provided that is operatively movable between an "open" position in which molten resin can freely flow through the melt channel 28 and exit through the outlet 29, and a "closed position" in which the molten resin is blocked from exiting the outlet 29 30 pieces. The rotary valve assembly 30 includes a closing head 24 that defines a valve body 32 . Defined within the valve body 32 is an outer bore 34 that bisects the melt channel 28 in a generally transverse direction.

A pair of end caps 38 are located partially within the outer bore 34 on opposite sides of the valve body 32 . Each end cap 38 includes a cylindrical insert portion 40 that extends into the outer bore 34 . Flange portions 46 on each of the end caps 38 limit the distance that the end caps 38 can be inserted into the holes 34 . The fastener 50 is used to securely mount the end cap 38 to the valve body 32 and to prevent the end cap 38 from rotating. The extension 52 on each of the end caps 38 is a hollow cylinder on the side of the flange portion 46 opposite the insertion portion 40 . Inner holes 48 having a smaller diameter than the outer holes 34 extend through the center of the end cap 38 such that each inner hole 48 is concentric with the outer holes 34 .

The outer bore 34 and inner bore 48 in each end cap 38 cooperate to define a valve seat 36 . The portion of the outer bore 34 between the two insert portions 40 defines a wider portion 42 of the valve seat 36 and each inner bore 48 defines a narrower portion 44 of the valve seat 36 . The wider portion 42 is preferably located within the center of the valve body 32 such that the melt channel 28 continues on opposite sides of the wider portion 42 . With the end cap 38 mounted to the side of the valve body 32 , in the presently described embodiment, each of the two inner bores 48 is longer than the outer bore 34 . However, it is also contemplated that the inner bore 48 may be sized to be longer or shorter than the outer bore 34 .

The spool 54 is rotatably positioned within the valve seat 36 . The spool 54 includes a thicker portion, ie, a central portion 58 within the wider portion 42 . On opposite sides of the central portion 58 are thinner portions coaxially aligned with the central portion 58 , namely end portions 60 , each of which is located within the inner bore 48 . A step 64 is provided between the central portion 58 and each end portion 60 . For example, the spool 54 may have a diameter of 54 mm in the central portion 58 and may have a diameter of 35 mm in each end portion 60, which is reduced compared to the continuous diameter spool 54 having the diameter of the central portion 58 The total surface area of the spool 54.

An aperture 70 is defined in the central portion 58 . When the spool 54 is in the open position, the bore 70 is aligned to be coaxial with the melt passage 28, thereby allowing the passage of molten material. When the spool 54 is in the closed position, the bore 70 is rotated away from the melt channel 28 such that a land 72 ( FIG. 2 ) on the spool 54 prevents molten material from flowing. Preferably, each of the end portions 60 extends completely through its respective bore 48 and past the outer edge 56 of the valve seat 36 . Both ends 66 of the spool 54 are adapted to be attached to an actuator arm 68 . Movement of the actuator arm 68 by means of an actuator (not shown) moves the spool 54 between the open position and the closed position. While the presently described embodiment shows the spool 54 having a pair of end portions 60 extending beyond the outer rim 56 , it is contemplated that a spool 54 with only one end portion 60 or no end portions 60 extending past the outer rim 56 may be provided.

The spool 54 is sized such that it can rotate freely within the valve seat 36 . As best seen in FIGS. 4, 5A and 5B, a gap 62 is provided between the sidewall of the spool 54 and adjacent portions of the outer bore 34 or inner bore 48 so that the actuator (not shown) is relatively small. The rotary valve assembly 30 is easy to open or close. In FIGS. 4, 5A and 5B, the size of the gap 62 is exaggerated for clarity purposes. For some molten materials, gap 62 allows the molten material to lubricate between the parts, thereby reducing the force required to actuate the valve assembly. However, leakage of molten material along the gap 62 and through the outer edge 56 remains an ongoing problem. A wider gap (eg, 0.02mm to 0.03mm) reduces component wear and actuation forces. Tighter gaps (eg, 0.01 mm to 0.02 mm) reduce leakage but may result in greater component wear and slower cycle times between open and closed positions. Furthermore, the use of a tighter gap 62 increases the heat-to-volume ratio of the resin in the gap 62, potentially burning molten material in this region. Carbonized resin builds up in gap 62 , adheres to the surrounding surfaces of valve seat 36 , and increases system friction, leading to degraded performance or component sticking.

In the presently described embodiment, a gap 62 is provided between the sidewall of the spool 54 and adjacent portions of the inner bore 48 ( FIG. 5A ) or the outer bore 34 ( FIG. 5B ). Because the annular cross-sectional area of the gap 62 between the inner hole 48 and the spool 60 ( FIG. 5A ) is smaller than the annular cross-sectional area of the gap 62 between the outer hole 34 and the spool 60 ( FIG. 5B ), it is the same as having Leakage is reduced compared to assemblies of constant diameter spools sized to fit central portion 58 (not shown).

Additionally, the pressure in the leaking molten material decreases as the molten material travels farther in the orthogonal direction from aperture 70 ( FIG. 3 ). Because the length (along the axis of rotation) of the opposing sealing surfaces on the valve plug 54 and valve seat 36 extends beyond the size of the valve body 32 due to the end cap 38 and end portion 60, leakage of molten material beyond the outer rim 56 is further enhanced. reduce. Given the reduced leakage effected by the extended sealing surface and reduced annular cross-sectional area, a wider gap 62 can be tolerated than would be the case with a continuous diameter spool 54 sized to fit the central portion 58 .

To assemble the rotary valve assembly 30, one of the end caps 38 is first removed. Next, the spool 54 is inserted into the valve body 32 with the pilot end portion 60 slid through the bore 48 over the remaining end cap 38 . Once in place, the removed end cap 38 can be reinstalled and secured by means of the fastener 50 . Non-rotational movement of the spool 54 is constrained.

Referring now to FIGS. 6A and 6B , another non-limiting embodiment of the present invention is shown generally at 130 . The rotary valve assembly 130 includes heating elements 74 (in the presently described embodiment, heating cartridges) distributed around the valve body 32 to maintain the temperature of the molten material. The heating elements 74 are distributed radially around the melt channel 28 and positioned away from the sealing surface around the tip portion 60 so that the leaking molten material is as cool as possible as it approaches the outer edge 56 .

Referring additionally to FIG. 7 , a cooling element 76 is provided to cool the end portion 60 near the end of the bore 48 using forced convection or natural convection. For example, air inlet 66 is operable to receive pressurized airflow from a hose (not shown). Forced air is circulated around cooling channels (not shown) and exhaust is directed out air outlet 70 . Alternatively, cooling element 76 uses a closed loop system using water or another cooling medium (not depicted). Passive cooling elements, ie heat sinks 78, may also be provided. In the embodiment illustrated in FIGS. 5 and 6 , fins 78 are formed in the extension 52 of one of the end caps 38 . In both embodiments, the cooling element 76 increases the viscosity of the leaking molten material as it approaches the outer rim 56, thereby reducing the leak flow.

Referring now to Figure 8, an additional embodiment of the present invention is shown. A spool 254 comprising a plurality of concentric grooves 192 across the surface area of each end portion 60 is provided. Depending on the viscosity of the molten material, the concentric grooves 192 enable a labyrinth sealing, further providing pressure drop in the leaking molten material, while also providing lubrication for spool rotation.

Referring now to FIGS. 9-11 , an additional non-limiting embodiment of the present invention will be shown generally at 230 . The rotary valve assembly 230 includes at least one wedge assembly 94 to reduce the gap 62 between the valve seat 36 and the spool 154 along at least one annular segment around the spool 54 . Each wedge assembly 94 includes at least one circumferential groove 84 and a piston ring 88 associated with each circumferential groove 84 . Circumferential grooves 84 are distributed along the surface of end portion 160 of spool 154 , with each circumferential groove 84 having a sloped sidewall 86 on its edge facing outwards (ie, towards the nearest outer edge 56 ). One of the piston rings 88 is located within each circumferential groove 84 . Each piston ring 88 has a complementary tapered side wall 90 complementary to the sloped side wall 86 on the circumferential groove 84 . Each piston ring 88 further has a series of spaced pressure grooves 92 opposite the tapered sidewall 90 . As the seeping molten material spreads out along the gap 62 toward the outer edge 56 , it begins to fill into the circumferential groove 84 via the pressure groove 92 cut in the piston ring 88 . Piston ring 88 is drawn outwardly against adjacent surface 93 on end cap 38 in a wedging action between sloped sidewall 86 and tapered sidewall 90, thereby reducing the surface area across piston ring 88 between spool 154 and Gap 62 between end caps 38 . Because the reduced clearance 62 occurs only on the surface area of the piston ring 88 and only when the molten material is pressurized, the overall increase in rotational friction and resin coking on the spool 154 is minimized. As the melt pressure acting on each piston ring 88 decreases, each piston ring 88 recedes back into its circumferential groove 84, reducing the rotational friction of the spool 154 back towards its original operating state.

Referring now to FIG. 12 , an additional non-limiting embodiment of the invention is shown generally at 330 . The rotary valve assembly 330 includes at least one wedge assembly 194 to reduce the gap 62 around the spool 54 . The wedge assembly 194 includes a tapered ring 96 on each end portion 60 adjacent to an end wall 98 on the end cap 38 . A collet (ie, threaded nut 100 ) is mounted onto complementary threads on extension 152 on end cap 38 . Threaded nut 100 includes a complementary internal taper 102 opposite taper 104 on tapered ring 96 . Thus, by tightening the threaded nut 100 around the end cap 38 , the wedging action between the mating tapered surfaces closes the gap 62 between the inner side surface 106 on the tapered ring 96 and the adjacent portion of the end portion 60 . Because the reduced gap 62 occurs only over the surface area of the tapered ring 96, the overall increase in rotational friction on the spool 54 and resin coking is minimized. Additionally, the threaded nut 100 can be loosened or tightened as desired.

Referring now to FIG. 13 , an additional non-limiting embodiment of the invention is shown generally at 430 . The rotary valve assembly 430 includes a valve body 132 adapted to receive only a single end cap 138 . On one side of the melt channel 28 , the valve body 132 delimits the outer bore 34 and the inner bore 48 . A step 112 is provided between the outer bore 34 and the inner bore 48 . On the other side of the melt channel 28 , the valve body 132 defines a peripheral bore 134 concentric with but wider than the outer bore 34 . Insertion portion 140 on end cap 138 is partially inserted into perimeter hole 134 , said insertion portion 140 being mounted to valve body 132 by fastener 150 . The insert portion 140 defines the inner bore 48 on the other side of the melt channel 28 and further defines the step 112 on this side. While the presently described embodiment shows the end caps 138 machined as separate pieces that are attached together, integrally formed end caps 138 are also within the scope of the present invention.

To assemble the rotary assembly 430 , the spool 54 is inserted into the valve body 132 after the end cap 138 is removed, with the pilot end portion 60 sliding through the inner bore 48 . Once in place, the removed end cap 138 can be reinstalled and secured by fasteners 150 . The spool 54 is fully restrained from rotational movement and cannot slide without loosening the end cap 138 .

Referring now to FIG. 14 , an additional non-limiting embodiment of the invention is shown generally at 530 . A rotary valve assembly 530 is provided having the recessed area 208 in one of the end caps 238 . (While the presently described embodiment uses only a single end cap 238, two end caps 238 could also be used). A wedge assembly 294 is provided to further reduce leakage. Wedge assembly 294 includes a pair of tapered rings, inner ring 210 and outer ring 212 within recessed region 208 . A spring plate 214 retains the two rings 210 and 212 within the recessed area 208 . The two rings 210 and 212 are complementary to each other and include opposing tapers 216 . Seepage of molten material along gap 62 causes inner ring 210 to slide off towards outer ring 212 . The wedging action between the inner ring 210 and the outer ring 212 reduces the gap 62 between each ring and the end portion 60 or its adjacent surface 220 of the bore 48 . Because the reduced gap 62 occurs only over the surface area of the two rings 210 and 212, operating friction on the spool 54 and the overall increase in resin coking are minimized.

Non-limiting embodiments of the present invention may provide a rotary valve assembly having a reduced amount of leakage. Non-limiting embodiments of the present invention may provide a rotary valve assembly having a reduced amount of resin coking. Non-limiting embodiments of the present invention may provide a rotary valve assembly with reduced actuation force requirements. Non-limiting embodiments of the present invention may provide a rotary valve assembly with a narrower closing head.

The description of non-limiting embodiments provides examples of the invention, and these examples do not limit the scope of the invention. It should be understood that the scope of the present invention is limited by the claims. The concepts described above may be adapted to specific conditions and/or functions, and may be further extended to a variety of other applications within the scope of the present invention. Having thus described non-limiting embodiments, it will be apparent that modifications and enhancements are possible without departing from the concepts described. Accordingly, what is protected by Letters Patent is limited only by the scope of the appended claims.

Claims (22)

1. A rotary valve assembly (30, 130, 230, 330, 430, 530) for an injection unit (20) comprising A valve body (32, 132) delimiting a melt channel (28) for a working fluid and an outer bore (34) laterally separating said melt channel (28) point; at least one end cap (38, 138, 238) mounted to said valve body (32, 132) and defining an insert portion (40, 140) extending into said outer bore (34), said valve body ( 32, 132) and said at least one end cap (38, 138, 238) cooperatively define a valve seat (36) transversely intersecting said melt channel (28), said valve seat (36) having a wider portion (42) bounded by a portion of said outer bore (34) and a narrower portion (44) bounded by an inner bore (48) of said at least one end cap (38, 138, 238) ; as well as a spool (54, 154) defining an orifice (70), said spool (54, 154) being rotatably mounted within said valve seat (36) and between said orifice (70) and said The open position of the melt channel (28) aligned for rapid transfer of the working fluid through the melt channel (28) is not aligned with the orifice (70) and the melt channel (28) aligned to prevent said rapid transfer of said working fluid through said melt channel (28) from moving between closed positions; and wherein said wider portion (42) of said valve seat is shorter than said narrower portion (44) of said valve seat. 2. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 1, wherein said insert portion (40) is coaxially mounted within said wider portion (42), said The wider portion (42) is defined within the valve body (32, 132). 3. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 1, wherein said spool (54, 154) includes said relatively a thinner portion within the narrow portion (44), and a thicker portion within the wider portion (42) of the valve seat (36). 4. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 1, wherein the wider portion (42) of the valve seat (36) is in contact with the melt channel (28) INTERSECTION. 5. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 1, wherein the valve seat (36) includes a second narrower portion (44), and the narrower A portion (44) and said second narrower portion (44) are located on opposite sides of said wider portion (42). 6. The rotary valve assembly (430) of claim 5, wherein the second narrower portion (44) is defined within the valve body (32, 132). 7. The rotary valve assembly (30, 130, 230, 330, 530) of claim 5, wherein said at least one end cap (38, 238) includes a A pair of end caps (38, 238) on opposite sides, and the narrower portion (44) and the second narrower portion (44) are both bounded by the pair of end caps (38, 238). 8. The rotary valve assembly (230, 330, 430, 530) of claim 1, wherein the gap (62) between the spool (54, 154) and the valve seat (36) is along the The length of the valve seat (36) decreases over at least one annular section. 9. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 8, wherein each of said at least one annular segment is located on said narrower portion (44) . 10. The rotary valve assembly (30, 130, 230, 330, 430, 530) of claim 8, wherein said at least one annular section includes, on an outer surface of said narrower portion, adapted to provide A plurality of concentric grooves (192) for a labyrinth seal. 11. The rotary valve assembly (230, 330, 530) of claim 1, wherein a wedge assembly (94, 194, 294) is located on the spool (54, 154) and is operable to reduce Said gap (62) on at least one annular segment of said spool (54, 154) is reduced. 12. The rotary valve assembly (230) of claim 11, wherein the wedge assembly (94) includes at least one circumferential groove (84) defined on the spool (154), and a piston A ring (88) is located within each of said at least one circumferential groove (84), said piston ring (88) being operable to direct said working fluid leaking over said gap (62) to said piston The ring (88) engages the adjacent surface (93) of the valve seat (36) upon application of force. 13. The rotary valve assembly (230) of claim 12, wherein each of said at least one circumferential groove (84) includes a tapered sidewall (90) on an outwardly facing edge, and Each piston ring (88) includes complementary tapered sidewalls (90) for sliding action thereon. 14. The rotary valve assembly (230) of claim 13, wherein each piston ring (88) defines a pressure groove (92) in a sidewall opposite the tapered sidewall (90). 15. The rotary valve assembly (330, 530) of claim 1, wherein a wedge assembly (194, 294) is positioned adjacent the outer edge (56) of the valve seat (36), the wedge The wedge assembly (194, 294) is operable to reduce the gap (62) between the spool (54) and the inside surface (106, 220) of the wedge assembly (194, 294). 16. The rotary valve assembly (330) of claim 15, wherein the wedge assembly (194) includes a tapered ring ( 96), and a collet having a complementary inner taper (102) retains said tapered ring (96) adjacent said outer edge (56) of said valve seat (36). 17. The rotary valve assembly (530) of claim 15, wherein a force applied to the wedge assembly (294) by the working fluid to the wedge assembly reduces the valve The gap (62) between the core (54) and the inner side surface (220) of the wedge assembly (294). 18. The rotary valve assembly (530) of claim 17, wherein said wedge assembly (294) includes a pair of opposing cones (116) on said spool (54) Conical rings, the pair of conical rings are retained by the side walls of the end cap (238) and the spring plate (118). 19. The rotary valve assembly (130) of claim 1, wherein a cooling element (76) is positioned proximate an outer edge (56) of the valve seat (36). 20. The rotary valve assembly (130) of claim 19, wherein the cooling element (76) includes cooling passages operable to circulate a cooling medium. 21. The rotary valve assembly (130) of claim 20, wherein the cooling element (76) comprises cooling fins (78). 22. The rotary valve assembly (130) of claim 1, wherein a heating element (74) is located on the valve body (32), the heating element (74) being remote from the valve seat (36) at all The narrower portion (44) is positioned.